LUMBAR PLEXUS AND BRANCHES. 497 



Its termination in the integuments of the buttock and abdomen, by means 

 of an iliac and a hypogastric branch, has been already mentioned (p. 416). 



b. The ilio-inguinal branch (</) arises with the preceding from the first 

 nerve, and issues from the psoas nearly at the same spot. Of smaller size 

 than the ilio-hypogastric, this branch courses outwards over the quadratus 

 and iliacus muscles towards the front of the crest of the hip bone, where 

 it pierces the transversalis abdorninis. The farther course of the nerve in 

 the abdominal wall, and its distribution over the scrotum and the groin, 

 are before noticed (p. 416). 



c. The genito -crural nerve (k] is distributed to the cremaster muscle 

 and the limb. It arises from the second lumbar nerve, and from the con- 

 necting loop between the first two ; it pierces the fibres of the psoas, and 

 descending on the surface of the muscle divides into the two following 

 pieces. Sometimes the nerve is divided in the psoas, and the pieces per- 

 forate separately the muscle. 



The cremasteric branch descends on the external iliac artery, and fur- 

 nishes offsets around it : it passes from the abdomen with the spermatic 

 vessels, and is distributed in the cremaster muscle. In the female the 

 nerve is lost in the round ligament. 



The crural branch issues beneath Poupart's ligament to supply the in- 

 tegument of the thigh. 



d. The external cutaneous nerve of the thigh (Y) arises from the second 

 nerve of the plexus, or from the loop between it and the third, and appears 

 about the middle of the outer border of the psoas. The nerve then crosses 

 the iliacus to the interval between the anterior iliac spinous processes, and 

 leaves the abdomen beneath Poupart's ligament, to be distributed on the 

 outer aspect of the limb. 



e. The anterior crural nerve (k) is the largest offset of the plexus, and 

 supplies branches mainly to the extensor muscles of the knee joint, and 

 to the teguments of the front of the thigh and inner side of the leg. 

 Taking origin from the third and fourth nerves, and receiving a fasciculus 

 also from the second, this large trunk appears towards the lower part of 

 the psoas, where it lies between that muscle and the iliacus. It passes 

 from the abdomen beneath Poupart's ligament ; but before the final branch- 

 ing in the thigh, the nerve furnishes the following twigs : 



Some small branches are furnished to the iliacus from the upper part of 

 the nerve. 



A branch to the femoral artery, whose place of origin varies much, is 

 distributed around the upper part of that vessel. 



f. The obturator nerve (n) appertains to the adductor muscles of the 

 thigh. Derived from the third and fourth nerves in the plexus, it is di- 

 rected beneath the psoas to the inner or pelvic border; escaped from be- 

 neath the muscle the nerve crosses the pelvic cavity below the external 

 iliac, but above the obturator vessels, and enters the thigh through the 

 aperture in the upper part of the thyroid foramen. Occasionally the ob- 

 turator gives origin to the following branch : 



The accessory obturator nerve (7) arises from the trunk of the obturator, 

 or from the third and fourth nerves of the plexus. Its course is along the 

 inner border of the psoas beneath the investing fascia, and over the hip 

 bone to the thigh, where it ends by joining the obturator nerve, and sup- 

 plying the hip joint. 



GANGLIATED CORD OF THE SYMPATHETIC. The lumbar part of the 

 gangliated cord of the sympathetic in the abdomen is placed on the side 

 32 



